This invention relates generally to a liquid level gauge, and more particularly to gauges commonly used for measuring liquefied petroleum gas (LPG) type liquids. The LPG is typically stored as a liquid under pressure in a tank or cylinder. A typical gauge for liquid level measurement is the type that utilizes a pivoting float arm having a float at one end and an opposing counterweight at another positioned on an opposing side of a pivot from the float. The pivoting float arm moves in response to changes in the liquid level inside the tank. As the float arm pivots, it rotates a gear assembly which turns a drive shaft located in a support arm that is connected to the float arm. The drive shaft is connected to a tank magnet which is magnetically coupled to a receiving magnet in a dial assembly. As the drive shaft rotates and rotates the tank magnet, the magnetic flux of the tank magnet rotates the receiving magnet which moves an external liquid level visual indicator, such as a pointer on a dial, or provides a signal for use by an electronic read out device. Examples of such gauges are disclosed in U.S. Pat. Nos. 6,089,086 and 6,041,650.
A continuing quest in the field is to develop more flexible designs that allows for rapid assembly and a reduction in inventory of component parts for the manufacture of gauges. There are many designs and sizes of tanks for storing liquefied gases. In the past, it was common to manufacture a number of gauges of a similar design in various sizes for use in the different tanks. Typically, the different sized tanks have a standard opening size for receiving the gauge assembly. This required many individual parts for the manufacture of different sized gauges. However, many different lengths of support arms and float arms were required by prior designs. Further, most of these parts had to be manufactured to close tolerances. This created a large inventory of parts to manufacture, store and inventory. Further, in other to economically manufacture the parts, they had to be manufactured in certain minimum quantities. For certain sizes of gauges in low demand a long period of time passed before the investment in inventory was recouped. One attempt to address this issue was the design of a gauge with an adjustable support member, such as the “One” gauge manufactured by Rochester Gauges which used an adjustable stem that was mated with an appropriate length float assembly.
In addition to the inventory problems, prior designs did not provide for the convenient alignment of the tank magnet on the end of the drive shaft with a base position of the float arm so that accurate readings will be transferred to the dial assembly. Such a feature is important so that when the gears connected to the drive shaft in the support arm and the gears connected to the float arm are attached, they are in a position that allows an accurate reading of the level of liquid in the tank. This alignment was done manually by rotating a round drive shaft until the position of the tank magnet on the drive shaft corresponded to the given location of the float arm. At that point, the drive shaft was staked to the gear, permanently attaching the gear to the drive shaft and ensuring that the alignment of the magnet did not change. The assembly process was subject to the potential to create inaccuracy in alignment and incorrect readings. This problem was addressed in part by the designs shown in U.S. Pat. Nos. 6,089,086 and 6,041,650, and the specific designs illustrated aid in properly aligning the magnet relative to the float position.
Prior designs however did not solve the problems of providing an easy to assemble, reliable gauge while achieving a reduction in inventory and the more efficient use of components. Prior designs have not addressed solving the problems associated with designs requiring a large inventory for the many different sizes of gauges.
There is a continuing need for a gauge design that reduces the requirement for inventory, but also provides for easy assembly while at the same time providing a construction that will allow the gauge to be reliable. The present invention has the advantages that it minimizes inventory needed to construct a wide variety of gauge sizes, provides for quick assembly, provides indexing of the shafts and magnets, allows for use of some parts having lower tolerances, and provides a construction that is reliable.